MRI is Effective for Assessing Chest Pain Due to Acute Coronary Syndrome

The “rule-in” process for chest pain generates an estimated $600 million per year in unnecessary in-patient expenses, and yet some patients’ acute coronary syndrome goes undiagnosed.

When a patient presents to the emergency room with chest pain, their acute coronary syndrome may include many different entities, for example, ST-elevation myocardial infarction (MI), non-ST-elevation MI, and unstable angina. Correct assessment of the chest pain is essential for appropriate treatment.

Even more worrying, recent estimates indicate that nearly 2% of patients with acute MI are inappropriately discharged from the emergency room after presenting with chest pain. These discharged patients have had MIs which are missed even though they have undergone proper testing.

In patients whose MI is missed, the mortality rate is around 16%. Therefore, the current diagnostic strategies imaging chest pain in patients presenting in the ER have shortcomings which need to be addressed.

Can cardiac MRI can accurately identify patients with acute coronary syndrome? A prospective study completed using 161 consecutive patients who presented to the ER with >30 minutes of chest pain compatible with myocardial ischemia seems to indicate that it can.

The patients studied also had an electrocardiogram not diagnostic of acute MI.

MRI was performed at rest within 12 hours of presentation, and included perfusion, assessment of left ventricular function, and gadolinium-enhanced MI detection. All patients were followed up at 6 to 8 weeks to ensure that no acute coronary syndrome was missed in the ER.

From the study results, resting cardiac MRI appears suitable for the triage of patients with chest pain in the ER. Performed urgently to evaluate chest pain, MRI accurately detected a high fraction of patients with acute coronary syndrome, including those with enzyme-negative unstable angina.

One important limitation to note is that with cardiac MRI, there is the inability to differentiate acute versus chronic MI. Both have similar delayed enhancement characteristics, and cannot be differentiated.

Cost-effectiveness may help our institutions gain more respect for this approach to chest pain assessment. If we are able to show a way to address the $600 million per year of unnecessary in-patient expenses used to work up acute coronary syndrome, then widespread use may be just around the corner.

The take-home message here: Resting cardiac MRI is suitable to triage patients with chest pain who present in the emergency room, and more effective cardiac imaging can most certainly save lives

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Reviewer: Clay R. Hinrichs, MD
Reference: Kwong RY, Ashussheim AE, et al: Detecting Acute Coronary Syndrome in the Emergency Department With Cardiac Magnetic Resonance Imaging. Circulation; 2003; 107 (February): 531-537